X0202 4 2006-05-18 0 0000315293 AON CORP AOC 0001145037 RYAN PATRICK G C/O AON CORPORATE LAW DEPARTMENT 8TH FLOOR, 200 EAST RANDOLPH DRIVE CHICAGO IL 60601 1 1 0 0 Executive Chairman Common Stock 2006-05-18 4 S 0 1400 35.66 D 8795694 D Common Stock 2006-05-18 4 S 0 600 35.84 D 8795094 D Common Stock 2006-05-18 4 S 0 200 35.90 D 8794894 D Common Stock 2006-05-18 4 S 0 100 36.02 D 8794794 D Common Stock 2006-05-18 4 S 0 100 36.00 D 8794694 D Common Stock 2006-05-18 4 S 0 100 35.92 D 8794594 D Common Stock 2006-05-18 4 S 0 100 35.86 D 8794494 D Common Stock 2006-05-18 4 S 0 200 35.85 D 8794294 D Common Stock 2006-05-18 4 S 0 1000 35.79 D 8793294 D Common Stock 2006-05-18 4 S 0 1000 35.78 D 8792294 D Common Stock 2006-05-18 4 S 0 500 35.82 D 8791794 D Common Stock 2006-05-18 4 S 0 400 35.81 D 8791394 D Common Stock 2006-05-18 4 S 0 2500 35.75 D 8788894 D Common Stock 2006-05-18 4 S 0 2000 35.72 D 8786894 D Common Stock 2006-05-18 4 S 0 1800 35.73 D 8785094 D Common Stock 2006-05-18 4 S 0 1500 35.74 D 8783594 D Common Stock 2006-05-18 4 S 0 3000 35.76 D 8780594 D Common Stock 2006-05-18 4 S 0 700 35.70 D 8779894 D Common Stock 2006-05-18 4 S 0 700 35.71 D 8779194 D Common Stock 2006-05-18 4 S 0 1100 35.62 D 8778094 D Common Stock 2006-05-18 4 S 0 600 35.60 D 8777494 D Common Stock 2006-05-18 4 S 0 1900 35.65 D 8775594 D Common Stock 2006-05-18 4 S 0 700 35.63 D 8774894 D Common Stock 2006-05-18 4 S 0 500 35.58 D 8774394 D Common Stock 2006-05-18 4 S 0 1500 35.80 D 8772894 D Common Stock 2006-05-18 4 S 0 700 35.67 D 8772194 D Common Stock 2006-05-18 4 S 0 1100 35.68 D 8771094 D Common Stock 2006-05-18 4 S 0 500 35.59 D 8770594 D Common Stock 2006-05-18 4 S 0 1800 35.55 D 8768794 D Common Stock 2006-05-18 4 S 0 1200 35.57 D 8767594 D The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 25, 2005. Form 1 of 4 /s/ Patrick G. Ryan 2006-05-22